The present invention relates to a current detection equipment and a semiconductor device, and more particularly, to a current detection equipment which detects a current flowing through a conductor in a semiconductor device, semiconductor device package or various kinds of electric circuit equipment by a magnetic induction or magnetic field detection, and the semiconductor device using the same.
A current detection equipment for detecting a current from the outside is required in order to measure a current flowing through a lead or a conductor provided in a semiconductor device, or various kinds of electric elements or electric circuits.
For example, the semiconductor device for electric power has evolved into the so-called “module type” with increase in capacity, and the module is becoming larger. However, unevenness of the internal current which originates in parasitic factors, such as an inductance, in a module arises. When the performance of the module is improved, for example by increasing a current capacity or by increasing the operation speed of the module, a destruction of elements in the module may arise owing to the unevenness of the current, and it is becoming a problem.
On the other hand, a current probe cannot be inserted in an inside of the module on the occasion of measurement of the current in a module type semiconductor device. For this reason, unless the internal structure is changed, measurement of current in a module type semiconductor element is practically impossible. On the other hand, if the internal structure of the module is changed in order to provide the conventional measurement equipment such as current transformers, since the inductance itself changes, conditions of measurement also changes and as the results the current to be measured is changed. This leads lower accuracy of measurement. For this reason, a minute current probe for measuring without changing the electrode structure inside a module etc. is being needed.
Conventionally, for detection of a short circuit or for feedback on gate voltage, the current is measured by using an element with a current sensor or by using a current probe called “CT (Current Transformer: current transformer)” etc.
The element with a current sensor has been developed in IGBT (Insulated Gate Bipolar Transistor). This IGBT chip has the structure where the emitter is divided into a divided emitter and a main emitter. In the case of this element, in the state where gate is ON, the current which is flowing through the main element can be estimated by detecting the voltage decrease at the resistance which is inserted between the divided emitter and the main emitter.
However, in this system, since a current sensing part is made as a part of the chip of IGBT, there are the following problems:
(1) Chip structure becomes complicated.
(2) The effective area of the chip becomes smaller.
(3) The output of the voltage decrease from the emitter resistance in the IGBT varies.
(4) The linearity between the current which actually flows, and an output is low.
(5) The output is not insulated.
Chip cost increases as a result of the above (1). The current which can be passed becomes smaller as a result of (2). Measurement accuracy falls as a result of (3). The design of a detection circuit becomes difficult and complicated as a result of (4). Insulating device such as a photo-coupler is required in order to insulate the output as a result of (5). Consequently, the output becomes binary (“1” and “0”), and analog values, such as a current value, cannot be fed back to the control side.
On the other hand, CT convergence the current magnetic flux generated around a conductor with a magnetic core, and detects the current as an electromagnetic induction current produced in a coil. However, the magnetic core has the following problems:
(1) In order to prevent the magnetic saturation in a large current condition, CT is enlarged.
(2) The inductance of the main circuit increases in accordance with the form of the core. As a result, current will increase by forming a current path different form original one when a large core of CT is inserted in the circuit.
Because of these problems, when CT is installed in a small semiconductor device, it is difficult to detect current correctly without affecting the operation of the semiconductor device.
As explained above, it was difficult to measure current correctly and easily, without affecting the operation in insides, of devices, such as a semiconductor device, with the conventional technology.